They have small green canisters on their backs that emit an unknown chemical weapon, which does no damage but slows the player and blurs the player's screen. These canisters make the same click as a claymore so some players confuse the two. The only time these canisters are deadly is when an already injured player tries to run away from enemies. They are usually placed by armories and/or near the player. They also emit gas on death. They appear to have little armor. This is shown by the fact that they are particularly weak against most weapons, being of the same health as a medium trooper. They also appear to have gas surrounding them, which can allow a player to spot them before they set them off. The canisters themselves appear not to have any sort of sensor visible on them, and it just blows up when a player gets near it, releasing a sizable amount of gas. Another way to notice them is that their weapons possess a distinctive sound, which is the PP2000's firing sound from Call of Duty: Modern Warfare 2. Overlord will not inform a player about Chemical agents unless the wave they are deployed is either the first wave they appear in during the game, or they set down their chemical mines.

The gas seems to have no effect on other enemies, even those without gas masks. Chemical Agents have gas masks and something that looks similar to an oxygen tank, containing gas. Chemical Agents will always use the PP90M1. They do not appear to use grenades, as they rely on their allies to utilize ordnance against a player.

Chemical Agents pose threats when working with other agents or other units, and it appears that they are more of a support unit rather than the mainline units that come after a player aggressively, as Chemical Agents, along with Claymore Experts, appear to take their time, planting chemical mines and Claymores around the map before engaging the player. Compared to most units, Chemical Agents do not work in conjunction with any unit consistently, rather working with whoever is there to protect them from the player, allowing them to set mines down in areas.

These units will be deployed at wave 13 on Tier Two maps, wave 18 on tier three maps, and earlier wave 9 on tier four maps, so players should prepare for the possibility of running into chemical bombs in choke points or armories. These units, whilst functioning identically to their Claymore planting counterparts, are apparently better armed, as the PP90M1 is more effective at range, compared to the PM-9 used by the Claymore experts. One thing the players should be aware of is the fact that enemy forces will deploy Claymore experts at the same time as Chemical Agents on later rounds, or early rounds, depending on the map the player is on, so players should be cautious about where they go, as the chemical mines will only slow them down, but claymores will most likely kill a wounded player who runs away from pursuing enemies.

Even though the death quote for Survival Mode says sometimes "It is beneficial to kill a Chemical Gas Agent when they are near other enemies", killing them near their allies will do nothing to benefit the player outside of obscuring the enemy and giving them a chance to maneuver without being seen. It may be possible that the gas was meant to affect both teams, and the gas affecting both teams was changed to only affecting the players team late in development.